Apparatus for drying materials



Nov. 17, 1925- .56 2

G. GRINDROD APPARATUS FOR DRYING MATERIALS Filed Feb. 28, 1920 4 2 Sheets-Shet 1 p I lNVENTO/Z 6202 76 Gnindrad,

ATTOBNE Y Nbv. 17,1925 1,562,229

G. GRINDROD APPARATUS FOR DRYING MATERIALS jiled 2b. 28, 1920 Y 2 Sheets-Sheet 2 IN VEN T0 Gearqc Grim fang ATTORNEY Patented N'ov. 1'], 1.925. v

UNITED STATES v ,1,562,zz9

PATENT oFFIcE'.

enonon eamnnon, or oconoivrowocfwrsconsm, AssIen'oa TO- cnima'r'ron MILK raonucrs coMrANY, or SEATTLE, WASHINGTON, ,A c'oRronA'rIoN or DELAWARE.

arrnim'rus FOR DRYING mn'rnamnsj 'App1ication filed February 28, 1920 Serial No. 362,054.

I To all whom it mdy co r w ern:

Be it known that I,'Gnoac1t GRiNDRoD,

I a citizen of the United States, and a resident of the city of Oconomowoc, in the county of lVaukesha and. State of \Visconsin, have invented at new and useful Improved Apparatus for Drying Materials, ofwhich the following is tion.

This invention relates to an ,improved apparatus for drying materials, and has for its primary object to provideasimple and effective heat distribution means'whereby a surface may be heated to a theoretically uniform temperature throughout its area.

In the operation'and control of many manufacturing processes it is necessary to accurately determine at various stages of the process the moisture or volatile constituents of the material being treated. This is usually accomplished by drying accurately weighed portions of the material on a plate heated to a suitable temperature. Generally in the drying of portions of organic products, 'such as condensed milk, Where some,,.

decomposition of the solids takes place, the unknown sample is dried, together with a sample of-known composition, which latter acts as a c0ntrol',-and the results are corrected according to the value obtained from the control sample. In order that accurate and reliable results may be obtained, it is, of course, essential that the two samples shall be subjected to precisely the same treatment and at the same temperature.

Heretofore in;v the practice of the art electrically heatedplates largeenough to accommodate a number of sample dishes have been used. These plates are arranged either in the open air or in vacuum chambers or ovens.

' It is desired thatthere shall be such a distribution of the heat over the area of the plate that each unit of the surface area will be at exactly the same temperature as every other unit of area, so that the dishes on the plate will receive exactly the same amount of heat, to within a fraction of a degree F.

Such electric heating for the purpose described has heretofore been almost universal because it seemed to give a better uniform heat distribution than any other means. But electric heating has been found tohave certain disadvantages, among which the following may be enumerated.

'. First, it is expensive, constituting a cona full, clear, and exact descrip with the current usually available, is frequently as high as 10%, whereasuniformity to within .1% lS- (1e SlI'ed- Especial and'somewhat complicated means of thermostatic control are therefore necessary, or else constant attention and regulation-by handis required.

Thirdly, while it is possible to-so distribute the resistance in an electric plate as to secure nearly, uniform heating, this unihas been found to'be only temporary formity V 1e resistance wires tend to crystallize since t and increase resistance in spots. -This abnormal condition resultslin the creation of hot spots on the surface area of the plate.

'Heretofore steam has not, be?) used for cause ofthe'difliculty in eflectin distribution of the heat to the surface bein heated, by means of a vapor or other liqui heating medium. It was usually found that ,there'would be a higher degree of heat at .the middleof the plate and at the point of inlet than at the corners and theedges of the .plate. 'Thesame trouble was also expericnced. when a radiator like piping was inserted within the hollow plate, viz, that the inlet; point would be much hotter than the outlet.

this purpose. to any appreciable extent bea uniform.

My present invention, therefore consists in the provision of an improved mea s'for equalizing the distribution of heat from steam, water or other vapor or liquid heating means to the surface of theplate being heat-z ed, so that the temperature over the, entire surface area of the plate will be exactly the same at all points; In other Words,by means of the present improved method I have secured a distribution'of'the heatto the plate surface which is theoretically uniform, whereas the heat distribution obtained by electricity or other means heretofore 'employed is only approximately-nniform..

Having the above and otherobjects in -view, the invention consists in the improved method and apparatus for the distribution of heat, as above characterized, and inthe form, construction and'relative arrangement. of the several parts of such apparatus as lustrated in the accompanying drawings and will be hereinafter more fully described, il-

subsequently incorporated in the sub-joined claims. j

In the drawings wherein I have disclosed several practical embodiments of apparatus through the medium of which the present invention may be successfully practiced,

and in which similar reference characters designate corresponding parts throughout the several views Figure 1 is a top plan view of a hot plate such as is generallyused in drying processes,

to which I have above referred.

Figure 2 is a bottom plan view of the plate illustrating the arrangement of the double coil heating pipe therein.

Figure 3 is a longitudinal section taken on'the line 33 of Figure 2.

' plate may be of any other desired polygonal moreparticularly to Figures 1, 2 and 0 shape or of circular form in plan.

Within the hollow hot plate and between the marginal flanges thereof the heating pipe or tube generally designated by the numeral 7 is arranged.- This pipe is bent upon itself at its central portion, as shown at 8, and

from this point two sections of the pipe are extended in spaced parallel relation to each other in the form of reversed bends or coils, as at 9, the longer dimensions of said coils preferably, though not necessarily, extending longitudinally of the hot plate. The two ends of the pipe 7 are extended through one of the marginal end flanges 6, and it may be assumed for the purposes of this explanation that the steam, hot Water or other vapor oi fluid heating medium has its inlet tov the circulating coil 9 through the pipe or tube end'lO, and its outlet through the end 11 of the pipe, as indicated by the arrows in Figure 2. After the heating pipe 7 has thus been arranged within the hot plate, the hollow plate between the flanges (3 is completely filled with a metal of high heat conducting capacity.

In practical operation it will-be apparent from the above description that the steam or other heating fluid in traversing its course through the tube or pipe 7 repeatedly ,7

parallels itself in itspassage in and out through the pipe coil. Therefore, if the ingoing fluid has a temperaturefiof 230 F.,- and the outgoing fluid-has a temperature of tubes.

210 F., the temperature at the middle of the tube or pipe, or at the point 8 will be 220 F., and at the ends of the tube the temperatures of the ingoing and outgoing fluidequalize each other, so that the" temperature transmitted through the/plate above them is exactly/the ,average of the temperatureinside of the parallel tube sections, or 220 F. It is evidentthat all other points throughout the length of the double pipe or tube coil will show thesame outs ward temperature, since the temperature transmitted is the average of theingoing and outgoing temperatures of the fluid-currents, and at all points these averages are the same. 'l.h-us, in this manner it is seen that a theoretically uniform distribution. of temperature to the surface of the plate is obtained In Figures 4, a? and 6 of the drawings I have illustrated another embodiment of ap paratus in which-the same principle of par-' allcl heating currents is employed. In this case I use. inner and outer tubes '12 and 13 respectively, the said tubes being coiled together longitudinally within the hollow plate, as at 14. The end 15, ofthe large outer tube terminating within the hot plate is closed, while the adjacent end of the inner tube 12 is open. If desired these tubes may be formed in a series of Se aratesectionsand conriected by suitable'elbows or return bends In this'modified construction of the apparatus it may be-assumd that the steam or other heating fluid enters through theiuner pipe or tube 12, and traverses the several'coils on this tube, being finally emitted from they end.of said tube into the closed end of'th'e outer tube 14. From this point the fluid travelsin a reverse direction between the walls of the outer and inner However, it is manifest that if desired the steam -.or other fluid may enter through the pipe 13 and return through the inner pipe 1% In either case the-differences in temperaturebetween the'ingoing and outgoing currents are equalized and the temperature transmitted outward is the mean of temperatures of the ingoing and outgoing currents. rThis mean temperature is necessarily'the same throughout the length'of the double tube.

It is not essential that a hollow plate ofthe type referred to shall be used, as the. heating tube .or tubes may be placed be- 1 neath a metal plate upon which the metals to be heated are arranged, or-the heating means may be embodied in the plate structure by casting or otherwise'forming the plate around the tube. I 1 While, as previously stated, my invention has for its primary purpose to provide a means for uniformly heating samples of materials which areto be tested for their 1 volatile content, another purpose of this 1 tities than has heretofore been possible, and 7 invention is to providea means for uniforml drying various materials 1n larger quanfor providing uniform temperatures at other places desired. Thus my improvedmethod of heat distribution, as above described, is especially applicable to the drying ofv materials in a vacuum shelf drier, especially where the materials are of organicnature, and the drying tem rature must necessarily be uniform throug l out the dryin area.

7 The invention is also readily app icable to rotary, vacuum' and atmospherie driers where it is desired to maintain a uniform leat temperature within the drying cylin-- From the foregoing description con-- sidered in connection with the accompany- ,ing drawings, the eonst'ruction and manner of operation of the several described em bodiments of the apparatus, as well'as the practical advantages residin in my improved method of heat distri ution will be readily understood. It will be apparent that by the use ofsteam or other vapor or fluid heating medium for such purposes, the costof maintenance and operation, particularly in cases where such drying processes are employed on a, large' scale may be materially reduced.

, Another important" consideration resides in the fact that the uncertainties accompanying the use of electrical means in such dry ing processes is entirely obviated, and higher as my invention, 1 have s'gned m efiiciency, productive of more accurate and reliable results, is obtained.

While I have ing drawings several possible constructions ofapparatus for accomplishing the intended purpose, it is, nevertheless, to be understood that the apparatus may also be exdisclosed in the accompanyamplified in numerous other alternative con 7 thereto, and having a series of inlet bends and a series of return bends extending longitudinally of said plate, the correspond-' ing bends of each series being arranged in "the same plane and adjacent to each other.

2. In combination with a hot plate, means for.heating the surfaceof said plate to a uniform temperature throughout its area consisting of inner and outer'p'ipesformed into a heating coil and arranged in proximity to said plate, saidpipes constituting a contlnuous circulating means for a fluid heating medium entering through one of the pipes and leaving through the other pipe. g

In testimony that I -claim the foregoing name.

GEORG Gm DROD. 

